3o6 wherry: acidity and alkalinity 



The usefulness of methods in which computation begins at the 

 neutral point in describing reactions has been urged by Walker 

 and Kay for natural waters/ by L. J. Henderson^ for biological 

 fluids, and by the writer for soils. ^ The plan adopted by the 

 first two authors has been criticized by Clark and Lubs^ as "very 

 inadequate," but that depends on the point of view. The 

 methods here proposed, which represent an extension of those 

 just referred to, are contrasted with the usual ones in table i ; 

 they appear to the writer quite adequate to express the relations 

 involved, and to possess several distinct advantages, as pointed 

 out in the discussion of the table. 



The first five columns of table i need no comment, as they 

 represent simply a statement of well-known methods of de- 

 scribing reactions; but the remainder require some explanation. 

 Under the proposed concentration method, as headings of col- 

 umns 6 and 7 the terms specific acidity and specific alkalinity^ 

 are used, since the unit, instead of being i gram-equivalent per 

 liter, as in the usual methods, is the number of gram-equivalents 

 per liter of each ion present in a standard substance, namely 

 pure water at ordinary temperature, which is practically 10-'. 

 The actual numbers corresponding to the powers of 10 repre- 

 senting the reactions likely to be met with in soils have been 

 inserted in columns 6 and 7. 



The headings of the potential columns are also new; as these 

 values may well be called chemical potentials, the letter X, 

 representing the Greek letter chi, the initial of chemical, is applied 

 to them.^ It may be noted here that only the first of these 

 columns need be used, if in the definition of chemical potential 

 the sign of the ion is included; that is, when a given number is 



* Journ. Soc. Chem. Ind. 31: 1013. 1912 

 "8016110646: 73. 1917. 



' Journ. Wash. Acad. Sci. 6: 675. 1916. 8: 591. 1918. 

 ^ Journ. Bacter. 2:14. 1917. 



* Walker and Kay calkd them relative acidities and alkalinities; the writer in 

 previous publications has used the term intensity of acidity and alkalinity, but it is 

 better to limit the conception of intensity to potentials. Acidivity and alkalivity 

 might be used if desired, 



* For the suggestion of this symbol, as well as for much additional assistance in 

 the preparation of this paper, the writer is indebted to Dr. E. Q. Adams of the Bureau 

 of Chemistry. i 



